The option to "Launch slave agents via Java Web Start" is missing from new node configuration, how can I add it to the options menu?
This question was asked elsewhere: https://stackoverflow.com/a/38740924
You have to enable the TCP port of JNLP agents to enable this option for slaves.
Manage Jenkins > Configure Global Security > TCP port for JNLP agents
In my case, the answer can be found in another question I asked in the same matter and it seems like the problem is in outdated Jenkins documentation.
In 1.x version it was called "Dumb slave" and in modern versions "Permanent Agent". It is exactly the same.